The present invention relates generally to the programming of programmable sensors, and particularly to the programming of Hall effect sensors while the sensors are connected with other circuitry.
A variety of sensors have parameters that are programmable by, for instance, applying momentary high voltage pulses to the sensor. The high voltage pulses effectively xe2x80x9cburnxe2x80x9d into the sensor the final, desired values of the parameters, e.g. gain.
For example, highly functional Hall effect sensors are available that have digitally programmable gains and offsets. The programming process is carried out by applying calibration signals which temporarily set the gain and offset at initial values, applying a known input, e.g., a magnetic field, to the Hall effect sensor and then measuring the output of the sensor or the output of a circuit to which the sensor is connected. This output is compared to an expected output. The sensor is then recalibrated with successive offsets and gains in an iterative manner until the expected output is obtained within a tolerance band. These final values may then be burned into a permanent memory of the Hall effect sensor, allowing the Hall effect sensor to retain the programmed values in the event of a power cycle.
Problems exist in programming such sensors whether the programming is done prior to connecting the sensor to a circuit or subsequent to connection of the sensor into a circuit. For example, if the sensor, e.g. Hall effect sensor, is programmed before being connected into a given circuit, any errors in the Hall effect sensor itself or in the installation of the sensor (e.g., tilt errors) can be considered additive to the rest of the circuit error to produce a total circuit error.
Potentially, the total circuit error can be reduced by programming the sensor after being mounted and connected to the applicable circuitry. Parameters, such as gain and offset, can be programmed to compensate for errors in the other circuitry. This results in a total circuit error that is much less than that obtained when programming the sensor prior to connection in the circuit. Because of the relatively high voltage pulses required to program the sensor, however, other circuit elements can be damaged if the programming is done after connecting the sensor into the circuit. For example, in many Hall effect sensor applications, the output of the Hall effect sensor is immediately presented to precision signal conditioning circuitry. This circuitry typically is sensitive to high voltages and may suffer a decrease in accuracy, or even destruction, if exposed to the high voltage pulses required for programming.
Accordingly, it would be advantageous to have a system and method for programming sensors, such as Hall effect sensors, after connecting the sensor into appropriate circuitry but without damaging sensitive elements of the circuitry.
The present invention features a method of programming a programmable sensor connected into a desired circuit. The method includes electrically connecting a programmable sensor into a circuit that is susceptible to damage by voltage pulses necessary to program the sensor. The method further includes adjusting parameters of the programmable sensor to compensate for potential errors in the circuit, and directing voltage pulses to the programmable sensor to permanently program a desired value for the parameter. The method further includes preventing the voltage pulse from damaging the circuit.
According to another aspect of the present invention, a method is provided for programming a programmable Hall effect sensor that is electrically connected into a circuit disposed on a printed circuit board. The method includes presenting a known input, such as a current or magnetic field to the programmable Hall effect sensor. The method further includes measuring a total output signal of the circuit, and iteratively adjusting at least one parameter of the programmable Hall effect sensor until the total output signal is within a tolerance band. The method further includes maintaining the programmed parameters at the desired values in the non-volatile memory of the Hall effect sensor. The method also includes protecting the circuit and its components from damage while the programming high voltage pulse is applied to the programmable Hall effect sensor.
According to another aspect of the present invention, a system is designed to facilitate the programming of a programmable device by a series of voltage pulses. The programming is performed while the device is electrically connected to a circuit having components that normally would be damaged by the pulses. The system includes a fixture having electrical contacts designed for conductive contact with the circuit intermediate the programmable device and a component susceptible to damage, such as an op amp. The system further includes voltage limiting circuitry electrically connected to the contacts to divert the voltage pulse and prevent component damage.